Both shows have quite a lot of similarities. Both are a military-themed reality shows where reservists from different special forces compete for the best team title. Alongside Korean both also include non-Korean special forces operators - in Iron Squad 3 it is US special forces (USSF) team, while in the Soldiers three out of four team captains/mentors are non-Korean. Some of the participants also participated in both shows which includes (but are not limited to) 707's Hong Beom-Seok, UDU's Go In-ho and USSF's Wil Ravelo (he was a mentor/team captain in the Soldiers). I believe that if you liked one, you will most likely like the other show as well.